1. Field of the Invention
Embodiments of the present invention relate generally to a fan speed control system and more specifically to a system for controlling fan speed in a computing system that includes multiple components capable of dissipating heat.
2. Description of the Related Art
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A computing system typically has a processing unit to process data. In order to improve the computing speed of a computing system, one approach is to integrate multiple processing units into a computing system. However, a processing unit consumes power and releases heat when it operates. This heat dissipation problem worsens if the computing system includes multiple processing units. Therefore, incorporating a cooling system in the computing system to take the released heat out of the computing system is essential to prevent the components in the computing system from malfunctioning or even burning down due to overheating.
A cooling system may include a fan. A fan typically generates noises and consumes power. If the speed of the fan cannot be adjusted and simply operates at full speed all the time, then the fan tends to make undesirable levels of noises and consume unnecessary amount of power. In addition, the life of such fan may be shortened.
FIG. 1 illustrates a conventional computing system 100 including three graphic processing units (GPUs), a first GPU 110, a second GPU 120 and a third GPU 130, that dissipate different levels of heat. The first GPU 110, the second GPU 120, and the third GPU 130 are associated with a first pulse-width modulation (PWM) signal 112, a second PWM signal 122, and a third PWM signal 132, respectively. A multi-channel fan controller IC 140 controls the operating speed of a fan 150 according to the respective PWM signal associated with each GPU.
The multi-channel fan controller IC 140 passes a specific PWM signal associated with a particular GPU dissipating the highest level of heat among the first GPU 110, the second GPU 120 and the third GPU 130. The fan 150 receives the specific PWM signal and adjusts its speed accordingly. In FIG. 1, the fan 150 is capable of interpreting a PWM signal passed through the multi-channel fan controller IC 140 directly. However, such fan capable of interpreting a PWM signal directly and the multi-channel fan controller IC are not a cost effective solution to a low cost computer system.
To further reduce cost, another conventional system avoids using a multi-channel fan controller IC and a fan capable of interpreting a PWM signal and instead uses a DC voltage controlled fan. FIG. 2 illustrates a computing system 200 including one GPU 210 and a DC voltage controlled fan 250. The GPU 210 dissipates heat and associates with a PWM signal 212. The PWM signal 212 is transferred to a DC voltage V214 at a node 214 by a resistance 220 and a capacitor 230, therefore, the DC voltage V214 is associated with the PWM signal 212. When the PWM signal 212 changes because of the operation of the GPU 210, the DC voltage V214 is changed accordingly. The DC voltage V214 is then amplified by an amplifier 240 with a fixed amplified ratio to generate an amplified voltage V216 at a node 216 which is strong enough to drive a fan 250.
In FIG. 2, the speed of the fan 250 is directly controlled by the amplified voltage 216, rather than the PWM signal 212. This type of fan is typically called as a DC voltage controlled fan and cheaper than the fan capable of interpreting a PWM signal directly. However, lacking of a component capable of selecting a highest voltage among different voltage sources, such as the multi-channel fan controller IC 140 illustrated in the FIG. 1, a DC voltage controlled fan and its control circuits cannot be used in a computing system including multiple processing units because the control circuits cannot control the speed of the fan 250 for a specific processing unit dissipating the highest level of heat among all processing units.
As the foregoing illustrates, what is needed is a system for controlling fan speed in a computing system that includes multiple processing units and addressing at least the problems set forth above.